gwsnr calculates gravitational-wave (GW) Signal-to-Noise Ratio (SNR), essential for population simulations and hierarchical Bayesian inference with selection effects. The package eliminates computational bottlenecks through sophisticated interpolation techniques, Just-in-Time (JIT) compilation, and parallel processing. It offers multiple optimized backends tailored for different hardware configurations: a numba backend for multi-threaded CPU performance and JAX (ascl:2111.002) and mlx backends for GPU acceleration. gwsnr integrates easily into existing workflows. It is used by the LeR package (ascl:2503.040) for simulating lensed and unlensed GWs, allowing researchers to incorporate fast SNR computations with minimal overhead.